ISO 21542:2021 — Building Construction: Accessibility and Usability of the Built Environment
Supporting accessible information within ISO 21542 environments
What this is
ISO 21542:2021, “Building construction — Accessibility and usability of the built environment”, is an international standard covering the design and construction of accessible, usable buildings, including access, circulation, egress and fire evacuation. Unlike UK-specific standards, it is internationally recognised — useful for organisations operating across multiple countries, or wanting to reference an international benchmark rather than a UK-only one.
Who it applies to
Building designers, owners and operators of non-domestic buildings internationally (with some guidance for residential common areas). Particularly relevant to organisations wanting a globally recognised accessibility reference rather than a jurisdiction-specific one — for example airport, transport or retail groups operating in several countries.
What kind of instrument this is
An International Standard (ISO) — voluntary unless adopted or referenced by national regulation, planning guidance, or a specific contract. Frequently used as a procurement or design benchmark, and referenced by national standards bodies when developing local equivalents.
Specific requirements relevant to announcements and accessible communication
- Clause 5.1 (Orientation and information), including 5.1.2 Levels of information — how information is made available to building users.
- Clause 5.5 (Signage), 5.5.1–5.5.14 — visual, tactile and Braille signage provisions.
- Clause 5.7 (Acoustics), including 5.7.3 Hearing enhancement.
- Clause 5.8 (Emergency warning systems, signals and information), 5.8.1–5.8.5 — covering general provisions, emergency warnings, audible emergency warnings, visual emergency warning signals, and fire emergency warning systems specifically.
- Clause 10.4.2 (Hearing enhancement systems), within the rooms-and-spaces section.
- Clause 11 (Fire safety and evacuation), 11.1–11.4 — ISO confirms this covers accessibility during both normal egress and evacuation in fire conditions.
What organisations are expected to do
- Provide clear, multi-format orientation and wayfinding information (Clause 5.1).
- Provide accessible signage (Clause 5.5).
- Consider hearing enhancement in relevant spaces (5.7.3, 10.4.2).
- Ensure emergency warnings are both audible and visual (5.8.3–5.8.4), not audible-only.
Which requirements AnnounceAgain can help address
The Clause 5.1 expectation for accessible information provision, for routine PA-style announcements only — not the certified fire alarm system covered separately under 5.8.5 and Clause 11 (see sections 8–9), and not the dedicated hearing-enhancement/induction-loop systems addressed under 5.7.3 and 10.4.2, which AnnounceAgain does not provide (see section 9).
How AnnounceAgain addresses them
- Converts routine PA announcements to text automatically, giving building users a visual equivalent to spoken information.
- Makes translated, replayable text available on personal devices, so information is not lost the moment it is spoken.
- Applies to routine, non-emergency PA announcements only. AnnounceAgain has no role — primary or supplementary — in fire alarm, emergency warning, or evacuation communication; that remains entirely the responsibility of certified equipment (see section 9).
Requirements AnnounceAgain does not satisfy by itself
- Must not be relied on as a visual emergency warning system under 5.8.4, or as a fire emergency warning system under 5.8.5, in any capacity — primary or supplementary. Those require dedicated, tested, fail-safe certified systems.
- Does not cover tactile/Braille signage (5.5), general wayfinding infrastructure (5.1.2, 6.3.2), or physical fire evacuation infrastructure (Clause 11.4).
Requirements needing certified hardware or other measures
- Certified fire alarm and emergency voice communication systems (5.8.5, Clause 11) — see the separate BS 5839-8 / BS EN 50849 datasheets.
- Dedicated hearing enhancement / induction loop installations (5.7.3, 10.4.2).
- Tactile and Braille signage production, and physical evacuation infrastructure (refuge points, evacuation lifts) under 11.4.